1. Field of the Invention
The present invention relates to an improvement in a one-way clutch used with a transmission of a motor vehicle, an agricultural machine, construction equipment, an industrial machine and the like, particularly an automatic transmission of a motor vehicle and performing a function such as back stop. Further, the present invention relates to a method for manufacturing a cage for holding a one-way clutch.
2. Related Background Art
In general, a one-way clutch used with an automatic transmission includes outer and inner races which are rotated relative to each other and is designed so that rotational torque is transmitted in only one direction by engaging sprags or rollers for transmitting torque between the outer race and the inner race with cam surfaces provided in a track face of the outer or inner race. Further, idle rotation is performed in a reverse direction.
In the one-way clutch of this kind, there is provided an annular cage having a plurality of window portions for holding the sprags as torque transmitting members. The cage is provided with elastic pieces so that desired drag is generated between the elastic pieces and the outer race by elastically engaging the elastic pieces with an inner periphery of the outer race, with the result that, immediately after the relative rotation between the outer and inner races changes from an idle rotation direction to an engagement direction, the sprags can transmit the torque between the outer race and the inner race.
FIGS. 5 and 6 show an example of a conventional cage having elastic pieces. FIG. 5 is an axial sectional view of the conventional cage and FIG. 6 is a partial enlarged view showing details of the elastic piece of FIG. 5. A substantially annular cage 24 is provided with a plurality of window portions 28 along a circumferential direction. A part of a column portion separating the window portion 28 from an adjacent window portion 28 is cut and bent radially outwardly to form an elastic piece 26.
As shown in FIG. 6, the elastic piece 26 includes two axial bent portions 29. The bent portions 29 are bent radially outwardly to afford desired dragging torque to an inner peripheral surface of an outer race.
In order to generate the dragging torque moderately, it is requested to design so that a repelling force of the entire elastic pieces has a desired value. To this end, there have been proposed (1) adjustment based on a bending amount of the elastic piece and (2) adjustment based on the number of elastic pieces.
The adjustment based on the bending amount to achieve the fact that the repelling force of the entire elastic pieces has the desired value is disclosed in Japanese Utility Model Application Laid-open No. 63-115637 (1988), Japanese Utility Model Publication No. 1-40345 (1989) and Japanese Utility Model Application Laid-open No. 5-94538 (1993), for example. Further, the adjustment based on the number of elastic pieces is disclosed in Japanese Utility Model Publication No. 1-40345 (1989). As a method for manufacturing a cage for holding the one-way clutch, a technique disclosed in Japanese Patent Application Laid-open No. 5-296266 (1993) is known.
However, in the above-mentioned conventional method, it was difficult to set the repelling force of the entire elastic pieces delicately. For example, in an arrangement in which a width of each column portion is great, the repelling force per elastic piece is great, with the result that, if the adjustment is performed on the basis of the number of elastic pieces, influence of each elastic piece will become too great. Further, also in an arrangement in which the width of the column portion is small, similarly, the delicate adjustment of the repelling force is limited.